Rotary switch



Dec. 13, 1938, H. BROADWELL 2,140,126

ROTARY SWITCH Filed Dec. 15, 1955 3 Sheets-Sheet' 1 lNl ENTOR H. BROADWE L L ATTOPNE Y talented Dec. 13, 1938 UNITED STATES" PATENT OFFlCE comer swrrcn 1 Application December 13, 1935, Serial No. 54,197

4 Claims. (01. zoo-105) This invention relates to electromagnetic switching devices and particularly to rotary switches which are adapted to be advanced step by step in either direction.

5 One of the objects of the invention is the provision of a durable and reliable circuit control ling switch mechanism of the rotary two-way step-by-step operated type. Another object is the provision of a. compact and emcient rotary two-way step-loy-step switch having many posi tions.

One feature of the invention is s rotary switch having two driving mechanisms, each consistin of an electromegnet, a ratchet, a driving pawl and a holding pawl, eechoperetion of one magnet lacing eflective to advance the shaft of the switch one step in one directionv oi rotation and each operation of the other magnet lacing efiectlve to advance the shaft in the opposite direction, the two holding powls being eflective when neither of the electromcgnets is energized to-locl: the shaft and cams in whatever position they are standing. Upon operation of either of the electromegnets and immediately prior to engagement of the assoelated driving pawl with its ratchet, the holding pawl for the other retchetis disengaged there-= from.

Another feature of the invention is e, rotary switch comprising e. shaft, s. cam mounted on the shaft for rotation therewith, and sset oi contact springs which are particularly designed for operation Icy a shallowliit com to make cost tive and continuous electrical contact at the time and for the interval desired.

A. switch, constructed in accordance with this invention, is illustrated in the drawings which form a. part of this specification.

Referring to the drawings:

Fig. l is 9. side view of the switch with. the near side of the cover cut away;

Fig. 2 is a. top view of the switch taken on lines iZ-t of Fig. l; I

Fig. 3 is s. top view of the switch taken on lines 3-3 of Fig. i;

Fig. c is a front view of the upper portion of the switch taken on lines 4-4 of Fig. i;

Fig. 5 is a iront view of the lower portion of the switch as modified to include a rheostet; and

Fig. e is s. side view of the lower portion of the modified switch shown in Fig. 5.

The frame of the switch consists of a. metal plate M, a heavy metal middle frame member 93 to the trout of plate ii loy screws M, end two horizontally disposed heavy meml Lrlstec l6 and It icstened to the middle frame member i3, one at each end by screws l1. This framework is clearly shown in Figs. 1 and 3. One or more open slots i2 are provided in each end of mounting plate H for use in removabiy fastening the switch to a vertical support, such as an equipment frame. A metal cover it, which together with mounting plate ll wholly encloses the switch, is fastened to frame members l5 and i6 by thumb screws 59 in screw holes to. A soft rubber gasket 23 between the open edge of the cover, the spring pile-up blocks and the mounting plate renders the enclosure dust-proof.

Extending vertically in. front of the middle frame member l3 and supported at each end by plates l5 and 56 is e. shaft 24 on which are mounted a. plurality of circular motel discs 25, herein referred to es cams. The cams are separated by spacers it end are fixed to the short by at key 21. The end portions to of shaft 2c, which portions are of reduced diameter, are ro== tatably supported by ball bearings, each or which comprises an inner ball race to, an outer race 33 and balls 36. Washers 2t separate the inner ball races from the uppermost and lowermost cams, and nuts ti are screwed onto threaded portions of the shaft 23 outside the inner ball races 89. it pin fixes the cositicn of the nut to prevent loosening during use. The outer ball races 33 are supported circumieiem tielly by' sleeves 3 8, the horizontal dances of which are fastened to plates l5 and fit icy screws 35. Rings 3'! screwed into the end plate memlo rs l5 and it serve to position the shaft vertically so that the cams are in alignment with. their esseciated springs. The rings 3? are locked in proper position by flanged nuts the loosening of nuts 38 is yrevented by forcing the edge of each into a slot extending radially under the flange the-opposing end plate to or it. The threaded portion of the ring 3'5 at the lower end of the shaft is solid since the shaft does not need to extend through the plate it, tout the threaded portion of the ring at the upper end of the shaft is drilled to permit the sheft to extend through plate t5, ratchet wheels 5i and 52 losing keyed on this end oi the shaft shove the plate as. An index wheel 53 is fastened onto the threaded end portion E6 of the shaft, shove the rstchetsv by a nut 64. The teeth of ratchet 58 are adapted for use in rotating the shaft 25 in one direction and the teeth of ratchet 52 are adapted tor use in rotating the shaft in the other direction.

Sets of contact springs are provided, eech set being associated with e difierent one oi the cams 26, the spring sets for adjacent cams being mounted on opposite sides of the middle frame member l3 as is best shown in Fig. 3. Each set of springs includes an actuating spring 42 and a pair of contact springs 43 and 44 on each side of the actuating spring 42, all of these springs being fixed in a spring pile-up block fastened by screws 4| to the middle frame member I3. The contact springs 43 and 44 of each set extend through the block 46 and through an opposing hole in the mounting plate II .to form the soldering lugs by which each of the pairs of contact springs is connected in the circuit to be controlled thereby. The rubber gasket 23 surrounds the holes through which the soldering lugs extend, so that each of the blocks 40 engages the gasket and forms a. dust-tight joint. The free end of the actuating spring 42 is bent over at right angles to its length to engage the periphery of the associated cam so as to close the contacts of one pair of springs 43 and 44 upon engaging the periphery at or near points of maximum radii and close the contacts of the other pair of springs 43 and 44 upon engaging the periphery at or near points of minimum radii. The cam contour provides for follow in the contact springs to insure good con- .tact. The forward end of each of springs 44 is anchored by. its projecting lug 46 and a screw 49 to the middle frame member l3, these two springs of each set being properly spaced at this point by an insulating sleeve 41 through which the screw extends. Washers 48 serve to insulate these springs from the screw 49 and frame member l3. A bifurcated lightweight contact spring is welded to each of the springs 44 at the anchoring point, the portion of each spring 44 which extends forward beyond the anchoring point serving as a stop to limit the follow of its bifurcated contact spring 45 when not in engagement with the free end of its associated spring 43. A clearance between the bifurcated springs 45 and the extending portions of the springs 44 is provided by an offset in the springs 45 near'the welding point. The extending portion of each of springs 44 is T-shaned the width of the spring being reduced between the anchoring point and the end which is bent toward the springs 45 to provide clearance for insertion of an adjusting tool; the reduced width also facilitates bending to adjust the follow of spring 45. Springs 45 are giventhe desired initial tension and the end of spring 44 provides a definite stop as near as possible to the point of. contact between spring 45 and spring 43 so that there is a fast build-up of contact pressure before spring 45 is moved away from engagement with the end of its associated spring 44. The possibility of chatter due to a slow build-up of pressure is thereby eliminated. By the anchoring of springs 44 and the use of the short lightweight bifurcated springs 45, positive and chatterless contact with the long and heavier springs 43 is insured with only a low contact pressure and minimum cam lift. The low cam lift permits cams of smaller diameter and,

therefore, smaller electromagnets than would otherwise be necessary. Mechanical vibration is minimized by the heavy frame. To facilitate maintenance, a numbering lug 39 is provided for each set of springs, which lug is held between the. heads of screws 4] and the spring pile-up block 40, the cams and associated sets of springs being thereby identified by letter, A, B, C, etc., printed on the front face of the lugs. With the cover removed, these identifying letters are visible upon looking back along each side of the switch.

In addition to the aforementioned ratchets 5| and 52, the mechanism for rotating and controlling the rotation of the shaft. and cams step by step in one direction or the other, comprises driving pawls 6| and 62 controlled by the armatures 14 of two electromagnets, the retaining pawls'55 and 56,'and overthrow stops 69. Each electromagnet comprises a coil 1|, magnetic core 12, U-shaped pole-piece 13, armature 14, and a non-magnetic four-legged bracket 15. The coil of each electromagnet is wound between spool heads 16, the core is fastened within the associated U-shaped pole-piece 13 by a screw 11, the pole-piece is fastened to the four legs of the associated U-shaped bracket 15 by screws 18, and the bracket for each electromagnet in fastened to the mounting plate II by screws 19. The armature of each electromagnet is pivoted on a pin 80 which extends vertically through the inner edge of the armature, the ends of the pin being fixed in the inner legs of the associated bracket 15. The rear ends of arms65 and 66, on the forward ends of which are attached the driving pawls 6| and 62, are bent upward to engage and be respectively fastened by, rivets to the rear surface of the armatures 14. For each electromagnet, a back stop pin 8| and lock nut 82 permit adjustment of the gap between the end of core 12 and the face of armature 14, the armature being biased by a spiral spring 83 so that the associated driving pawl is normally disengaged from the teeth of the-associated ratchet wheel, one end of spring 83 being fastened to the lug end 84 of the inner upper leg of bracket 15 and the other end to an L-shaped arm 85 screwed to and extending forward from the armature 14. The retaining pawls and 56 are irregularly shaped levers pivoted respectively on pins 51 and 56 fixed in plate IS. The pawls 55 and 56 are identical but are reversely mounted on plate l5 so that pawl 55 engages ratchet 5| and pawl 56 engages ratchet 52. The ends of these pawls remote from the ratchets are fastened by springs 59 to posts 60 fixed in plate I5 so that both pawls are normally in engagement with the ratchets 5| and 52 and the shaft and cams are, therefore, locked in whatever position they happen to be. The ends of these pawls are extended forward beyond the point at which the springs are attached to facilitate hand operation during the testing and adjusting of the switch. Upon energization of the coil of either electromagnet, the armature 14 is actuated, the forward end of the associated arm or 66 being thereby moved toward the ratchet 5| or 52. Before the associated driving pawl engages its ratchet, the retaining pawl must be dis-- engaged from the other ratchet. To th'isend, a lug 61 projects downward from the end of arm 65 to engage, as soon as arm 65 begins to move toward ratchet 5|, an opposing lug of the retaining pawl 56 so that the movement of arm 65 disengages pawl 56 from ratchet 52 before driving pawl 6| engages ratchet 5|. A like lug 68 projects upwardly from the end of arm 66 to engage,

-as soon as arm 56 begins to move toward ratchet 52, an opposing lug of the retaining pawl 55 so that the movement of arm 66 disengages pawl 55 from ratchet 5| before driving pawl 62 engages ratchet 52. The overthrow stops 69, fastened by screws 10 to the plate l5 limit the advance of the ratchets to exactly one step in response to each operation of the associated electromagnet. The ends of coils 1| are connected to the soldering lugs 86 of a pile-up block 81 which is fastened by L brackets 86, and screws to the mounting H6, the hub part of which is keyed on the lower. end of shaft H5. The shaft is enlarged to form' a collar which rests on the upper surface of the plate IIll. an index wheel adjustably held by a nut H8 plate II. The soldering lugs 86 extend out through a hole in the mounting plate and the block 8'! fits down onto the rubber gasket 23 to exclude dust.

A pointer Bil is fastened by screws 89 to the pole piece l3 to mark on the index wheel 53 the position in which the shaft and cams are resting. A glass index window 22 fastened in the cover it by a frame 'zl 'opposite the indexwheel enables the reading of the position in which'the switch is standing without removing the cover. This window is made dust tight by a rubber gasket around the frame 2i. l

The above described switch is particularly adapted for use in gain control for toll telephone lines. A switch is provided for each line, the cutting in or cutting out of resistance pads being controlled by the cams in the various positions of the switch. Switches having forty-one positions, that is, a zero or normal position and adapted to take twenty steps ln either direction from the normal position meet present commercial requirements. To prevent excessive drain in case all of the individual switches were moved simultaneously, a master switch may be provided to control the individual switches in groups, the various groups being operated successively. The master switch may be controlled by a Wheatstone bridge circuit, one arm of which includes a, pilot line similar to those whose gain is to be controlled. Changes in the resistance of the pilot line due to temperature variation cause an unbalance oi the bridge thereby causing the master switch to he stepped in one direction or the other as the case requires. One such Wheatstone bridge control circuit is disclosed in Patent 2,017,654 issued to J. A. Coy et al., October 15, 1935. The master switch may have a number of normal positions and once started. in either direction continues to rotate automatically until the next normal position is reached, all of the groups of individual switches being thereby successively moved as required. Thus, a master switch having forty-two positions might be used without waste of positions and with equally timed cycles of advance, for either six or for seven groups of individual switches. It is, of course, necessary that the balance of the control circuit for the master switch be automatically restored by the movement of the switch. To this end, the switch of Figs. 1, 2, 3 and 4 may be modified as shown in Figs. 5 and 6 by extending the mounting plate, adding a rheostat below the plate l6, and by extendin and coupling the shaft of the switch by a reduction gearing to the shaft of the rheostat to secure the required movement of the rheostat brush for each advance of the master switch from one normal position to thenext and To permit extension of the lower end 28 of shaft 24, there is a hole through the screw-end of lower ring 31, and the shaft extends through this hole far enough below plate IE to permit spur gear I Ill to be keyed onto the end of the shaft. The added rheostat comprises a. rectangular metal mounting plate I01 fastened parallel to the frame plate- I6 by metal sleeves I08 and the screws I09, a frame I ID of insulating material, such as Bakelite or hard rubber, fa.stened to the mounting plate I01 by screws I I I, a. winding II! of high resistance wire, binding post terminals H3 and H4, a shalt I 5 extending through the center of -frame III), and a brush On the shaft H5 above the collar is screwed onto a threaded portion of the shaft. The spur gear I04 which is staked onto the upper end of the shaft H5 is coupled to the spur gear IBI on the end 28 of shaft 24 by the spur gears I92 and N33. The hub of gear 502 fits tightly over the hub of gear I t3 and both rotate together on the sleeve I06 which is fixed by pin 505 to plate iii. The hole through sleeve M6 is eccentrically placed and the end is of hexagonal shape so that the sleeve may be turned to adjust the position oi gears Hi2 and 903 and thereby limit the backlash. A set of soldering lugs E23, a pair of contact springs H2, and an actuating spring l2i, are fixed in a pile-up block Hid, which block is fastened by screws to the mounting plate it. The free end of the actuating spring normally engages a stud H9 protecting downward from the binding post Hi3 so that the contacts of springs 622 are closed. The brush it carries a stud lit which, when the brush has reached the limit of its motion in either direction, engages the end of spring iii to open the contacts springs i252.

What is claimed is:

i. In a switching mechanism, a base plate, a

shaft rotatahly mounted thereon, a disc cam on said shaft tor rotation therewith, means for re tating said shaft and cam from any one oi a plurality of positions of rest into any other of said positions, a spring pile-up comprising an 'said member being fixed in said block so as to maintain the engagement between the free end of said member and said earn, the forward end of a first one of said contact springs being tree and tensioned toward said actuating member, the second oi said contact springs being further fixed at a point near its forward end, and a more flexible contact spring welded to the second contact spring at said point and extending forward .to engage the free end of said first contact p ng.

2. In a switching mechanism, a base plate, a shaft rotatably mounted thereon, a disc cam on said shaft for rotation therewith, means for rotating said shaft and cam from any one'of a. plurality of positlonsof rest into any other of said positions, a spring pile-up comprising an insulating block fastened to said mounting plate and a pair of fiat contact springs fixed near one end in said block in spaced and parallel relation and extending forward from saldblock toward said cam, a spring actuating member, one end ofsaid member engaging the'perlphery of said cm, a.

fiat spring extension of the other end 0! said member being fixed in said block so as to main engage the free end of said first contact spring,

the portion of said second contact spring which extends forward beyond said point being curved toward the free end of said more flexible contact 5 spring to form a stop for limiting the follow of the free end of said more flexible spring.

3. In a switching mechanism, a base plate, a

shaft rotatably mounted thereon, a .disc cam on said shaft for rotation therewith, means for ro- 1 tating said shaft and cam from any one oi a;

plurality of positions of rest into any other of said posi'zions, a spring pile-up comprising an insulating block fastened to said mounting plate '-antl a pa r of flat contact springs fixed near one 15 end in se id block in spaced and parallel relation and extei @ding forward from said block toward said cam -a spring actuating member, one end of said member engaging the periphery of said cam, a flat spring extension of the other end of 20 said member being fixed in said block so as to maintain the engagement between the free end of said member and said cam, the forward end of a first one of said contact springs being free and tensioned toward said actuating member, 25 the second of said contact springs being further fixed at a point near its forward end, and a more flexible contact spring welded to the second contact spring at said point and extending forward to engage the free end of said first contact spring, the portion of said second contact spring which extends forward beyond said point being bent toward the free end of said more flexible 5 contact spring to form a stop for limiting the follow of the free end of said more flexible spring, the extending portion of said second contact spring being of reduced width intermediate said point and its free end. 10

4. In a rotary circuit controlling device, a shaft, driving means comprising an electromagnet, a ratchet and a driving pawl for rotating said shaft in one direction, driving means comprising another electromagnet, ratchet and driv- 5 ing pawl for rotating said shaft in the other direction, a holding pawl normally engaging one of said ratchets for preventing rotation in one direction, and a like holding pawl normally engaging the other of said ratchets for preventing 2o rotation in the other direction, each of said driving pawls having a projection efl'ective just before the driving pawl engages its associated ratchet for disengaging the holding pawl from the other ratchet.

' HOWARD BROADWELL. 

